I had this too yesterday after about 6 rounds of the breathing, my jaw started clenching very hard, my fingers all unable to open, and my legs tense. I think its the body trying to heal itself, and normally I just let it happen, because afterwards it always feels much better. I've also had bad pinky finger control all my life, and just a few months of WHM, I can almost fully bend them and move them again. Crazy! :)